This paper presents a comparison of two approaches to finite element modeling of the dynamic behavior of a cable-stayed bridge. The bridge considered in this study is the Cape Girardeau Bridge, which has a composite deck composed of two steel girders along the edges spanned by a concrete slab. The first model of the deck assumes of a rectangular cross section with lumped masses at the deck level, while the second model includes additional lumped masses used to model the torsional behavior of the deck. Modal characteristics of the two models are compared to examine the effects of neglecting the shape of the cross section. The second model is shown to offer improved torsional responses, because the locations of the mass center and shear center are correctly accounted for in the model.